In a prior art tool replacement system, a tool replacement arm that copes with carry-in and carry-out of tools is provided at a machining center side, a tool conveyance apparatus reciprocates between the tool magazine and the tool replacement arm while holding a tool, and realizes acceptance of a tool from the tool replacement arm.
However, instead of directly accepting a tool between the tool conveyance apparatus and the tool replacement arm, such a design example exists, in which an intermediate holding portion is provided at a position within the range of turning of the holding portion at both side end portions of the tool replacement arm, and a tool is carried in the machining center by transferring the tool to the end portion side of the tool replacement arm while temporarily holding the tool transferred from the tool conveyance apparatus, and conversely, return of the corresponding tool is completed by transferring the tool to the tool conveyance apparatus after the tool replacement arm accepts the tool carried out from the machining center.
In this connection, it takes a predetermined duration of time for the tool conveyance apparatus to convey a tool from the tool magazine to the tool replacement arm and to return the tool, which is separated from the tool replacement apparatus, to the tool magazine.
However, operation times required for tools in a machining center are diverse, a case where the operation time is shorter than the time required for the tool conveyance apparatus to convey the tool to the intermediate holding apparatus occurs.
In such a case, with a tool intended to be operated next after the tool requiring such a shorter operation time, since the operation of the tool requiring a shorter operation time already ends at the point of time when the next tool is transferred to the position of the tool replacement arm by the tool conveyance apparatus, a so-called waiting time may occur in the machining center until the machining center commences its own operation.
As a matter of course, where such a waiting time frequently occurs, the operation efficiency in the entire process is necessarily lowered.
Taking attention on such a shortcoming in the prior art tool replacement system, such a configuration is disclosed in Patent Document 1, in which an intermediate magazine, for holding a plurality of tools sequentially between a tool arm, which is capable of replacing tools, is installed between the tool magazine and the machining center, the tool conveyance apparatus transfers tools from the intermediate magazine to the tool replacement arm and the corresponding intermediate magazine accepts tools from the tool replacement arm while the tool conveyance apparatus accepts tools from the intermediate magazine while reciprocating between the intermediate magazine and the tool magazine.
In the configuration according to Patent Document 1, since, with respect to all tools, transfer and carry-in of tools into the machining center and carry-out and return of the tools from the machining center are realized based on replacement between the intermediate magazine and the tool replacement arm, and all the tools planned to be operated are held in the intermediate magazine, no waiting time occurs, and efficient tool operation can be realized.
However, in the above-described configuration, the intermediate magazine is required to hold even tools, for which no waiting time occurs in order to hold, since all the tools are held in the intermediate magazine. As a result, the number of tools that the intermediate magazine must hold is necessarily increased, and it is necessary that the intermediate magazine has a large space therefore.
However, the arrangement situation of the machining center and tool magazine does not necessarily allow a large space for the intermediate magazine.
Patent Document 1 Japanese Published number of Unexamined Patent Application Hei-08-187640